Migration affect the population of the two particular areas. It increases the population of the place (new place), where people migrate in search of good facilities and decreases the population of the area where people migrate from. It is an unnatural cause that changes the population. 0.0
According to the Out Of Africa hypothesis, which is currently the dominant view in paleoanthropology and related fields, humans (Homo sapiens) evolved on the African continent and then spread to the rest of the world via migration. From their, they evolved slightly differently, for example having slightly different facial features.
